Mattress



FIG. 1 is a front perspective view of a mattress showing our new design;

FIG. 2 is an enlarged view of the encircled portion shown in FIG. 1;

FIG. 3 is a right side view thereof; and,

FIG. 4 is a front view thereof.

The contrast between the grey-filled racetrack-shaped elements and the remainder of mattress sidewall represents a contrast in appearance only and does not represent any particular color, material, or texture. Portions of the mattress are shown separated by break lines to indicate indeterminate length; the appearance of any portions of the mattress between the break lines from no part of the claimed design. The broken line showing of the remainder of the mattress represents environmental structure and forms no part of the claimed design. 

CLAIM The ornamental design for a mattress, as shown and described. 